/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/bits/popcnt.h"
#include "libc/stdio/stdio.h"
#include "libc/testlib/testlib.h"

unsigned naive(unsigned beg, unsigned end, unsigned size) {
  assert(end < size);
  assert(beg < size);
  assert(popcnt(size) == 1);
  if (beg == end) return size;
  if (end > beg) return end - beg;
  return (size - beg) + end;
}

unsigned fancy(unsigned beg, unsigned end, unsigned size) {
  return ((end - beg - 1) & (size - 1)) + 1;
}

TEST(favail, test) {
  unsigned i, j, n = 4;
  for (i = 0; i < n; ++i) {
    for (j = 0; j < n; ++j) {
      ASSERT_EQ(naive(i, j, n), fancy(i, j, n), "%u %u %u", i, j, n);
    }
  }
}
